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Transgenic mouse lines expressing the active form Akt gene under the control of the damage-induced neuronal endopeptidase (DINE) promoter were made from three different founder mice, and its neuroprotective potential against ischemic brain damage was investigated. Twenty-four hours after middle cerebral artery occlusion, two DINE-Akt-transgenic mouse lines displayed reductions of the infarcted area by 35% compared to the wild-type littermate. RT-PCR assays showed a high level of transgene in response to ischemic brain damage in these lines. These results suggest that the DINE promoter is a useful promoter, which responds to neuronal insults and that the Akt-induced neuroprotective effect against ischemic damage is potent in vivo.

It has been demonstrated that some of immediate early genes such as c-Jun are induced immediately and transiently following focal cerebral ischemia. Here we newly characterize the activating transcription factor (ATF)-3 as a focal ischemia associated immediate early gene. Using in situ hybridization and immunohistochemistry, we compared the expression profile of ATF-3 with those of ATF-2 and c-Jun after middle cerebral artery (MCA) occlusion. Focal cerebral ischemia induced two temporal and spatial patterns of ATF-3 expression. Early and transient induction of ATF-3 mRNA was observed in the core and margins of the cortex immediately after MCA occlusion. Late-onset and prolonged expression of ATF-3 mRNA and its protein were specifically identified in the peri-infarct cortex and thalamus where neurons survive at least 1 month. The expression profiles of ATF-3 and c-Jun were virtually similar, but c-Jun expression was also observed in other regions of the brain in control rats. Expression of ATF-2 was ubiquitously seen in neuronal cells throughout the brain in normal rats, but was suppressed in ischemic regions. Double immunohistochemical labeling revealed concurrent expression of ATF-3 and phospho-c-Jun in neurons. We conclude that the transcription factor ATF-3 is a suitable marker of neurons subjected to ischemic insult directly and indirectly, and that cooperative works of ATF-3 and c-Jun may be crucial triggers of various transcriptional responses to the ischemic insult.